The present invention relates to reciprocating scotch yoke drive mechanisms or translating rotary motion to linear motion, and more particularly for serving in a valve control for a water softener.
It is common to use a scotch yoke to translate rotational movements of a motor drive shaft to reciprocating linear motion. In the case of a control valve for a water softener, it is common to use a scotch yoke drive mechanism to translate rotational movement from the motor drive shaft to linear reciprocal movement on a guide. In such applications, the scotch yoke allows the motor to control the reciprocal linear displacement of a valve control piston.
Conventionally, the scotch yoke member is coupled to the rotary drive source to linearly reciprocate on a track located on the guide. Preferably, the yoke member and the track have a corresponding, complementary rectangular configuration. One disadvantage of known scotch yoke valve control mechanisms is that because of the rotary to linear movement translation and the force exerted from the drive shaft, it is difficult to securely maintain the scotch yoke member in the track on the guide. Another problem with this conventional scotch yoke valve control is that it causes excessive wear on the yoke member and the guide.
Still another problem is that the rectangular configuration often cannot maintain the alignment of the yoke member, such as through component misalignment, causing it to become disengaged from the guide. When that happens, control is lost over the piston shaft attached to the scotch yoke drive mechanism, and the valve cannot be controlled.
Accordingly, a first object of the present invention is to provide an improved scotch yoke mechanism which has better wearability.
Another object of the present invention is to provide an improved scotch yoke mechanism which can better retain the yoke member in the guide by its ability to maintain yoke alignment under a variety of angular stresses.
Yet another object of the present invention is to provide an improved scotch yoke mechanism which maintains alignment of the yoke member in the face of extended operational use and wear.